Method for forming semiconductor structure

ABSTRACT

The present invention provides a method for forming a semiconductor structure, the method includes: firstly, a substrate having a recess disposed therein is provided, wherein the substrate comprises a silicon substrate, next, a first element is formed in the recess and arranged along a first direction, wherein the first element is made of an oxidation semiconductor material, afterwards, a dielectric layer is formed on the first element, and a second element is formed on dielectric layer and arranged along the first direction, wherein the second element is used as the gate structure of a transistor structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 15/447,081, filed on Mar. 1, 2017, which is a divisional applicationof U.S. application Ser. No. 14/724,799, filed on May 28, 2015, now U.S.Pat. No. 9,627,547, issued on Apr. 18, 2017, and all benefits of suchearlier applications are hereby claimed for this division application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a method for formingsemiconductor structure and, more particularly, to method for forming asemiconductor structure combined with IGZO (In—Ga—Zn Oxide) materials.

2. Description of the Prior Art

Attention has been focused on a technique for formation of a transistorusing a semiconductor thin film formed over a substrate having aninsulating surface. The transistor is used in a wide range of electronicdevices such as an integrated circuit (IC) and an image display device(display device). A silicon-based semiconductor material is widely knownas a material for a semiconductor thin film applicable to a transistor,and within which, oxide semiconductor containing indium (In), gallium(Ga), and zinc (Zn) has been attracting attention.

A transistor including an oxide semiconductor film is known to have anextremely low leakage current in an off state. Nevertheless, currentarchitecture of integrating transistor having oxide semiconductor filmwith metal-oxide semiconductor (MOS) transistor is still insufficient inbringing out optical performance of the device. Hence, how to improvethe current fabrication flow for integrating oxide semiconductortransistor with MOS transistor has become an important task in thisfield.

SUMMARY OF THE INVENTION

The present invention provides a method for forming a semiconductorstructure, the method includes: firstly, a substrate having a recessdisposed therein is provided, wherein the substrate comprises a siliconsubstrate, next, a first element is formed in the recess and arrangedalong a first direction, wherein the first element is made of anoxidation semiconductor material, afterwards, a dielectric layer isformed on the first element, and a second element is formed ondielectric layer and arranged along the first direction, wherein thesecond element is used as the gate structure of a transistor structure.

The present invention further provides a method for formingsemiconductor structure, the method includes: firstly, a substratehaving an isolation region disposed therein is provided, next, a firstelement is formed in the isolation region and arranged along a firstdirection, wherein the first element is made of an oxidationsemiconductor material, afterwards, a dielectric layer is formed on thefirst element, wherein parts of the dielectric layer contacts thesubstrate directly, and a second element is formed on dielectric layerand arranged along a second direction, wherein the second element isused as the gate structure of a transistor structure.

The transistor structures of the present invention are combined with theoxidation semiconductor materials, especially with IGZO or CAAC-IGZO.Since IGZO or CAAC-IGZO have higher mobility than silicon, the leakagecurrent of a transistor structure made of IGZO is extremely low when thetransistor structure is under off state. In this way, the transistorstructure has low power consumption advantage. In summary, the presentinvention uses the IGZO or CAAC-IGZO to replace the channel region of atransistor structure, thereby improving the performance of thetransistor structure effectively.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 illustrate a method for fabricating a semiconductor structureaccording to a preferred embodiment of the present invention.

FIG. 6A shows the top view diagrams within the first region A, thesecond region B and parts of the third region C of FIG. 6.

FIG. 7A shows the top view within the first region A according toanother embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIGS. 1-6, FIGS. 1-6 illustrate a method for fabricatinga semiconductor structure according to a preferred embodiment of thepresent invention. As shown in FIG. 1, a substrate 12 is provided, inwhich the substrate 12 could be a silicon substrate, epitaxialsubstrate, silicon carbide substrate, or silicon-on-insulator (SOI)substrate, but is not limited thereto. In this embodiment, a firstregion A, a second region B and a third region C are defined on thesubstrate 12, wherein the transistor structure according to the firstpreferred embodiment of the present invention will be formed within thefirst region A in the following steps; the transistor structureaccording to the second preferred embodiment of the present inventionwill be formed within the second region B in the following steps; and aconventional transistor structure will be formed within the third regionC, used for comparing the transistor structures within the first regionA or within the second region B.

It is noteworthy that in the paragraph above, the first region A, thesecond region B and the third region C are defined on the substratesimultaneously, however, the present invention does not need to comprisethe first region A, the second region B and the third region Csimultaneously. In other words, if a structure only comprises thetransistor structure disposed within the first region A or onlycomprises the transistor structure disposed within the second region B,it should also be within the scope of the present invention. It will notbe noted again in the following paragraphs.

According to an embodiment of the present invention, a plurality ofdoped wells (not shown) and/or isolation regions 14 could be formed inthe substrate 12, the isolation region such as the shallow trenchisolations (STI). Besides, a dielectric layer is preferably formed onthe substrate 12, and the dielectric layer may be a single layerstructure or a multiple layers structure. In this embodiment, thedielectric layer includes a silicon oxide layer 16 and a silicon nitridelayer 18, but is not limited thereto, the material of the dielectriclayer can be adjusted according to actual requirements. In addition, thedielectric layer may comprise the hard mask and the etching stop layerduring the process for forming the isolation region 14.

Also, it should be noted that even though the fabrication process ofthis embodiment pertains to a planar type transistor, the fabricationprocess could also be applied to non-planar transistor such as FinFET,and in such instance, the element 12 shown in FIG. 1 would then become afin-shaped structure on a substrate. In this case, the dielectric layermentioned above can used as the hard mask for forming the fin-shapedstructure and the etching stop layer for forming the isolation region14.

Next, as shown in FIG. 2, at least one recess 20 is formed in thesubstrate 12 within the first region A and within the isolation region14 within the second region B respectively. The recess 20 can be formedthrough an etching process, but is not limited thereto.

As shown in FIG. 3, an oxidation semiconductor material 22 is thenfilled in each recess 20 within the first region A and within the secondregion B. Each recess 20 is filled by the oxidation semiconductormaterial 22, so as to form a plurality of first elements 24. Theoxidation semiconductor material mentioned above comprises In—Ga—Znoxide (IGZO) or c-axis aligned crystal IGZO, (CAAC-IGZO). Next, aplanarization process is performed, such as a chemical mechanicalpolishing (CMP) process, to remove the extra oxidation semiconductormaterial 22 on the dielectric layer (the silicon nitride layer 18), andto form a flat surface.

As shown in FIGS. 4-5, an etching back process E1 is performed, toremove the silicon oxide layer 16 and the silicon nitride layer 18.Preferably, the top surface of the substrate 12 is exposed, and at thistime, the top surface of each first element 24 is higher than the topsurface of the substrate 12. Afterwards, as shown in FIG. 5, an oxidelayer 26 is then deposited on the substrate 12, and covering each firstelement 24. The oxide layer 26 such as aluminum oxide (Al₂O₃), galliumoxide (Ga₂O₃), and HfO₂, but is not limited thereto. The oxide layer 26can protect the first element 24 disposed below, thereby avoiding thedestruction of the first elements 24 in the following steps.Furthermore, the oxide layer 26 can be used as the gate dielectric layerof a transistor structure, in other words, used as the dielectric layerwhich separates the gate region and the channel region from each other.

As shown in FIG. 6, a plurality of second elements 28 are formed withinthe first region A, the second region B and the third region C. Moreprecisely, the second elements 28 are used as the gate structures of atransistor device, covering on the oxide layer 26, and the material ofthe second element 28 may include polysilicon or metals. In addition,the manufacturing process for forming the second element 28 may beformed through a gate first process, a gate last high-k first process,or a gate last high-k last process. Those processes mentioned above arewell known to those skilled in the art, and will not be described indetail here.

In addition, FIG. 6A shows the top view diagrams within the first regionA, the second region B and parts of the third region C of FIG. 6. Asshown in FIG. 6, within the first region A, both the first element 24and the second element 28 (gate structure) are arranged along a firstdirection (such as Y− axis). Preferably, the area of the second element28 is larger than the area of the first element 24. Therefore, whenviewed in a top view, the second element 28 totally covers the firstelement 24. And the source/drain (S/D) regions or the epitaxial layer(not shown) are formed in the substrate 12 disposed on two sides of thesecond element 28. It is noteworthy that when viewed in cross sectionviews (such as FIGS. 1-6), even though the isolation region 14 is shownonly within the second region B, and not shown within the first regionA, actually as shown in FIG. 6A, the isolation region 14 is disposed inthe substrate and surrounding outside of the source/drain region.

In the present invention, please refer to FIG. 6 and FIG. 6A, twodifferent transistor structures are formed within the first region A andwithin the second region B respectively, and both of the transistorstructures are combined with IGZO materials. In other words, both ofthem comprise the first element 24 made of IGZO or CAAC-IGZO, and thefirst element 24 at least disposed in the channel region of thetransistor structure, namely disposed between the source region and thedrain region. Take the transistor structure within the first region A(the first preferably embodiment of the present invention) as anexample, the second element 28 is used as the gate structure, disposedon the oxide layer 26, and the source/drain regions are formed throughimplanting the substrate 12 disposed on two sides of the second element28. In this embodiment, the first element 24 is disposed in thesubstrate 12, directly contacting the substrate 12, and disposed betweenthe source region S and the drain region D, to be used as the channelregion of the transistor structure. IGZO (or CAAC-IGZO) has highermobility than silicon substrate does, thereby increasing the performanceof the transistor structure. Afterwards, the transistor structure can becombined with some semiconductor manufacturing processes, such asforming the interlayer dielectric (ILD), performing the silicide layer,forming the contact plugs, etc. The processes mentioned above are wellknown to those skilled in the art, and will not be described in detailhere.

In addition, FIG. 7A shows the top view within the first region Aaccording to another embodiment of the present invention. The differencebetween this embodiment and the transistor structure shown in FIG. 6A isthe first element 24 is only disposed between the source region S andthe drain region D, and does not extend to the isolation region 14surrounding outside. The structure should also be within the scope ofthe present invention. Others features of this embodiment are same asthose described above, and will not be redundantly described here.

Please refer to FIG. 6A again, showing the transistor structure withinthe second region B (the second embodiment of the present invention).The difference between this transistor structure and the transistorstructure of the first preferred embodiment is that in this embodiment,the isolation region 14 is disposed in the substrate 12, and the firstelement 24 is disposed in the isolation region 14, arranged along thefirst direction (such as Y-axis), and the second element 28 crosses overthe first element 24, arranged along a second direction (such asX-axis). Preferably, the second element 28 and the first element 24 arearranged orthogonally. Besides, when viewed in cross section views (FIG.6), the top surface of the isolation region 14 and the top surface ofthe first element 24 are on a same level, and the top surface of thefirst element 24 is higher than the top surface of the substrate 12. Inthis embodiment, the second element 28 is disposed on the oxide layer 26and used as the gate structure of a transistor structure, and the firstelement 24 disposed on two sides of the second element 28 is thenimplanted, so as to form the source region S/drain region D. Inaddition, the first element 24 disposed right below the second element28, namely the intersection of the second element 28 and the firstelement 24 is used as the channel region of the transistor structure.

Compared with conventional transistor structures, such as the transistorstructure formed within the third region C, the transistor structures ofthe present invention combined with the oxidation semiconductormaterials, especially with IGZO or CAAC-IGZO, has advantages. Since IGZOor CAAC-IGZO have higher mobility than silicon, and the leakage currentof a transistor structure made of IGZO is extremely low when thetransistor structure is under off state, the transistor structure haslow power consumption. In summary, the present invention uses the IGZOor CAAC-IGZO to replace the channel region of a transistor structure,thereby improving the performance of the transistor structureeffectively.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method for forming a semiconductor structure,comprising: providing a substrate having a recess disposed therein,wherein the substrate comprises a silicon substrate; forming a firstelement in the recess and arranged along a first direction, wherein thefirst element is made of an oxidation semiconductor material; forming adielectric layer disposed on the first element; and forming a secondelement disposed on dielectric layer and arranged along the firstdirection, wherein the second element is used as a gate structure of atransistor structure.
 2. The method of claim 1, wherein the oxidationsemiconductor material of the first element includes In—Ga—Zn oxide(IGZO).
 3. The method of claim 2, wherein the IGZO further comprisesc-axis aligned crystal IGZO (CAAC-IGZO).
 4. The method of claim 1,wherein the material of the second element includes polysilicon.
 5. Themethod of claim 1, wherein the first element directly contacts thesubstrate.
 6. The method of claim 1, wherein a top surface of the firstelement is higher than a top surface of the substrate.
 7. The method ofclaim 1, wherein the material of the dielectric layer includes aluminumoxide or gallium oxide.
 8. The method of claim 1, wherein the secondelement entirely covers the region of the first element.
 9. A method forforming a semiconductor structure, comprising: providing a substrate,having an isolation region disposed therein; forming a first elementdisposed in the isolation region and arranged along a first direction,wherein the first element is made of an oxidation semiconductormaterial; forming a dielectric layer disposed on the first element,wherein parts of the dielectric layer contacts the substrate directly;and forming a second element disposed on dielectric layer and arrangedalong a second direction, wherein the second element is used as a gatestructure of a transistor structure.
 10. The method of claim 9, whereinthe oxidation semiconductor material of the first element includesIn—Ga—Zn oxide (IGZO).
 11. The method of claim 10, wherein the IGZOfurther comprises c-axis aligned crystal IGZO (CAAC-IGZO).
 12. Themethod of claim 9, wherein the material of the second element includespolysilicon.
 13. The method of claim 9, wherein a top surface of thefirst element is higher than a top surface of the substrate.
 14. Themethod of claim 9, wherein the material of the dielectric layer includesaluminum oxide or gallium oxide.
 15. The method of claim 9, wherein thesecond direction is perpendicular to the first direction.
 16. The methodof claim 9, wherein a top surface of the isolation region and a topsurface of the first element are on a same level.
 17. The method ofclaim 9, wherein parts of the first element are disposed between asource region and a drain region of the transistor structure.